Effect of ocular residual astigmatisms on the correction of low refractive astigmatism using Q-value-guided LASIK

Session Details

Session Title: LASIK Outcomes and Refinements

Session Date/Time: Monday 09/10/2017 | 14:30-15:50

Paper Time: 15:25

Venue: Room 4.4

First Author: : J.Costa PORTUGAL

Co Author(s): :    F. Neves   L. Figueiredo   C. Santos   T. Pacheco   C. Arede        

Abstract Details

Purpose:

To evaluate the influence of the ocular residual astigmatism (ORA) on the refractive and the higher order aberrations (HOA) outcomes in patients with high myopia and low astigmatism treated with Q-value guided laser in situ keratomileusis (LASIK).

Setting:

Department of Ophthalmology of Centro Hospitalar Vila Nova de Gaia/Espinho, Portugal.

Methods:

This retrospective study included 46 patients (81 eyes) with high myopia (>2.50D) and low astigmatism (<2.25D) submitted to LASIK (Zyoptix® aspheric algorithm, Technolas217z100® system-Bausch&Lomb). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Patients were divided into two groups based on the ORA (ORA > mean - high ORA group; ORA ≤ mean - low ORA group). The patients were also divided into two groups based on the value of the ratio ORA/anterior corneal astigmatism (ACA). Efficacy was determined by comparing the index of success (IS) and the HOA between the groups, 3 months after surgery.

Results:

The mean preoperative cylinder, the mean residual refractive cylinder postoperatively, the mean ORA and ORA/ACA were -0.63±0.57D, -0.34±0.48D, 0.69±0.31D and 0.85±0.62D, respectively. Mean IS in the high and low ORA groups were 0.97 and 0.68, respectively (P=0.25); in the high and low ORA/ACA groups were 1.65 and 0.54, respectively (P<0.01). A correlation between ORA/ACA and the IS was found (ρ=0.48,p<0.05). We also found a correlation between the ORA/ACA and the difference between the topographic and the refractive astigmatism axes (ρ=0.42,p<0.01). No correlation was found between ORA, ORA/ACA and the HOA outcomes.

Conclusions:

The efficacy of astigmatic correction by LASIK (Zyoptix® aspheric algorithm) in patients with low astigmatism was significantly lower in eyes in which the preoperative refractive astigmatism is at a great extent located posterior to the anterior corneal surface (high ORA/ACA). However, the ORA and the ORA/ACA had no influence on the HOA outcomes. The ORA/ACA ratio, rather than the ORA, seems to influence the refractive outcomes of LASIK, and so it should be taken in consideration before performing refractive surgery.

Financial Disclosure:

NONE